Portable communication devices inform the wearer of an incoming call by ring tones or body sensory vibration generated by the rotation of an eccentric weight of a built-in vibration motor. The modes are switched as necessary. Some of game machines let the operator sense vibration generated by the vibration motor in the machine in the course of games for more fun.
Such kind of vibration motor is secured to a circuit board in the device/machine and generates and transmits vibration to the device/machine housing, whereby the wearer/operator of the communication device/game machine senses the vibration. Such an example is described in Japanese Patent Application Laid-open No. 2005-312282, wherein a built-in vibration motor is mounted on a circuit board in such a suspended manner that a motor case is clamped by a mountain frame radially from the outside around the upper half of the motor case and folded legs at the bottom of the mounting frame are bonded along the edges of a cutout formed in the circuit board.
In another example described in Japanese Patent Application Laid-open No. H11-234943, a vibration motor is mounted on a circuit board in such a manner that a cylindrical motor body is retained by a metal holder frame, an eccentric weight is fixed to one end of a motor shaft, creamed solder applied to the circuit board is melted in a heating furnace to secure the entire structure of the motor to the circuit board.
The above mounting methods do not ensure that the vibration motor is held by the mounting frame securely enough for the motor vibration generated by the rotation of the eccentric weight or for accidental drop of the device. Therefore, some countermeasures are provided such as spot welding between the mounting frame and motor case.
However, spot welding requires an expensive spot welding apparatus and produces spot residue or flash, which has to be removed. When the residue or flash remains, it may adversely affect the circuitry operation or motor rotation. Particularly, if the motor case is deformed by spot welding, it may cause a problem with the motor rotation.
On the other hand, there is an increasing demand for downsizing, flattening, and light-weight in recent portable communication devices and game machines. The vibration motors for generating body sensory vibration are not exceptional among many circuit parts and functional parts mounted in a limited space in the device. They are also required to be smaller. However, their downsizing has a limitation since they have to generate the necessary vibration.
It has therefore been desired to generate vibration having a large body sensory effect using the same vibration motor.